The Collaborative International Dictionary of English v.0.48:

Stadtholder \Stadt"hold`er\ (st[a^]t"h[=o]ld`[~e]r), n. [D.
   stadhouder; stad a city, a town + houder a holder.]
   Formerly, the chief magistrate of the United Provinces of
   Holland; also, the governor or lieutenant governor of a
   province.
   [1913 Webster] Stadtholderate